1. Field of the Invention
The present invention generally relates to contactors for testing electronic devices and, more particularly, to a contactor having contact electrodes which make a contact with terminals of an electronic device such as a semiconductor substrate (wafer) or a wiring board so as to perform an electrical test on the electronic device.
2. Description of the Related Art
In recent years, miniaturization of wiring and densification of circuits have been progressed in semiconductor devices such as, for example, a large-scaled integrated circuit chip (hereinafter referred to as LSI) so as to satisfy the demand for downsizing or upgrading of a product to which the LSI is incorporated. With such progression, miniaturization of LSI terminals and increase in the number of terminals are progressing rapidly.
For example, development is progressing so that the terminals of an LSI chip used by SIP (System In Package) may attain a pitch of about 20 xcexcm. Moreover, for the SIP application, the thickness of LSI chips has been rapidly reduced from, for example, 500 xcexcm to 100 xcexcm, 50 xcexcm or even 25 xcexcm. Accordingly, the following subjects are imposed also to contactors (probes) used for testing such an LSI chip.
1) It is necessary to develop immediately a contactor (probe) which can provide a good position accuracy (xc2x15 micrometers or less) in association with the miniaturization and increase in the number of LSI terminals.
2) Since LSIs become thinner, there is a possibility of breakage when an excessive contact force is applied thereto. For this reason, it is indispensable to control variation in a spring force of a probe to be as small as possible.
3) The area array type LSI has been increasing as arrangement of LSI terminals (terminals are arranged like a lattice over the whole area of LSI chip), and the contactor must correspond to the area array type LSI. That is, not only the conventional peripheral type LSI (terminals are arranged in the periphery of an LSI chip) but also the area array type LSI (terminals are arranged like a lattice over the whole area of an LSI chip) has been increasing, and a contact probe used for such an area array type LSI must have a higher density of electrodes than a probe for the peripheral type LSI. Thus, generally it is difficult to arrange and form the needles of the contactor.
4) In the case of a CSP (chip-size package) which has small pitch terminals or area array terminals, even for a packaged LSI, it has become difficult to maintain a previous cost of a contactor (socket) manufactured by a conventional technique.
There are two kinds of probe card systems.
A: Cantilever System (for peripheral type)
The cantilever system is a mainstream system in wafer probe cards. With respect to the structure of a probe of the cantilever system, ends (unbent side) of rod-like conductive members (needles) having bent ends are joined to terminals of a wiring board so that the bent ends of the rod-like members are pressed manually using an elongated tool so as to locate the bent ends within a desired range of position accuracy. The pitch of the ends on the wiring board side tends to be larger than that of the chip contact (needle tip)
B: Vertical Probe System (for area array type)
Since it is necessary to arrange pins in the shape of a lattice, a plurality of pins are arranged on a board fundamentally in a state where the pins are stood vertically to the board. However, if the pins are simply arranged vertically, the pins may contact with each other since a direction of bending of each pin, when it is pressed while being contacted with an LSI, cannot be the same. Thus, in a mainstream structure, the pins are previously bent in a predetermined direction. In order to make the pins stood together in large number, it is difficult to maintain a position of each pin while bending. Thus, the cost of the vertical probe system is more than twice the cantilever system.
A) Problems in the Cantilever System
I) There is a limitation in reducing the pitch.
A pitch of about 45 xcexcm is a limit since it is difficult to attain a positional accuracy of the needle tips (XY accuracy: less than xc2x15 xcexcm). As mentioned above, the final adjustment of the position of the needle tips is carried out by a small displacement by mechanical contact pressurization. There is an actual example in which the needle tip accuracy (xc2x110 xcexcm) is attained for the level of pitch of about 45 xcexcm. However, it is difficult to deal with a smaller pitch for the following reason.
(1) The distance between the needles is so small that a tool for position adjustment cannot be inserted.
(2) Even if the tool is inserted forcibly, it is difficult to maintain a movable area in which the needle tip can be displaced. Considering the spring back of the needle, it is impossible to maintain the movable area for obtaining a required displacement due to a relationship with adjacent needles.
II) It is difficult to obtain a uniform force with a narrow pitch.
Similar to the A) cantilever system, it is difficult to perform a work to adjust the height of the needle tips. If the needles are mechanically pressurized so as to adjust the height, a pressing tool tends to interfere with adjacent pins, which deteriorates easiness of work.
III) Basically, It cannot be applied to an area array type. It is considered that a two-row arrangement is a limit.
B) Problems in the Vertical Probe System
I) there is a processing limit in a narrow pitch.
Although a pitch of more than 150 xcexcm is mainly in use now, there is the same problem as A) cantilever system. That is, since there are adjacent pins on the right and left sides and front and back sides, which pins are obstructive, it is very much difficult to carry out a position correction with a high accuracy after the pins are formed on a board.
II) It is difficult to obtain a uniform force for a narrow pitch. Similar to A) cantilever system, it is difficult to adjust the pins in the same height.
III) Cost is high.
Since the adjacent pins becomes more obstructive as the pitch becomes smaller, it becomes difficult to perform a bending process (formation of bent portion), thereby inevitably increasing a manufacturing cost. Although there is a means to mount needles, which are previously bent, it is difficult to position the needles with the same direction of bending, thereby an increase in the manufacturing cost cannot be avoided.
C) Socket for CSP (Area Array of the Vertical Probe System)
Basically, there are problems similar to the problems of the above-mentioned B) vertical probe system. Additionally, it is necessary to plant small pins in a main part of a mold with higher accuracy as the pitch is decreased. The guide for pins, which accurately aligns the needle tips with the package terminals, requires a higher accuracy than a processing accuracy required for a conventional socket. In the case of CSP which uses solder balls as terminals, deformation of the solder balls become remarkable even when a contact pressure is slightly increased. Since the diameter and volume of each ball is decreased as the pitch becomes smaller, the degree of influence due to reduced pitch becomes remarkable, which causes a serious problem.
Thus, similar to the position accuracy of the pins, it is a subject to achieve a uniform contact force and reduce an increase in the cost. In order to solve the problems in the manufacturing methods of the conventional contactors as mentioned above, the applicants considered manufacturing a contactor suitable for a purpose of a prove by deforming needles or pins of the contactor using a laser bending technique.
As a conventional laser processing technology, the autumn convention academic lecture collection paper of the Japanese Society of Precision Engineering discloses on page 166 a laser processing technology which is considered to be applicable to a laser bending technique under the title xe2x80x9cmicro-forming of thin film metal glass by laser local heatingxe2x80x9d. Conventionally, laser processing has not been used for manufacture of contactors, especially for the processing method of a probe card. This is because although the laser processing technology is not particularly needed since the conventional technology was applicable in some degrees, there was a problem that desired processing cannot be performed with a simple technology that simply irradiates a laser beam.
In other applications, there are examples in which laser bending using a laser is used. However, the reason for the difficulty of application of laser processing to the manufacture of probes for LSIs or fine wiring boards is that these probes have an extremely fine or micro structure (for example, a tip has a diameter of less than 30 micron). Additionally, a plurality of small pins are arranged at a very small pitch (for example, less than 50 micron), and a high accuracy is required for the position of each pin (at least xc2x110 xcexcm). Although there were examples of applications to a bending process of individual parts or to a material or a board material having a width of a few millimeters, it was difficult to obtain a required processing or configuration by merely using a laser processing condition of other applications.
The following problems existed as the problems to be solved when applying the conventional laser technology to the processing of probes.
1) It was difficult to obtain displacement with high accuracy. If the resolution and variation in energy of laser irradiation are large, an unexpected large formation may occur in the probe.
2) In many cases, there was a restriction in a direction of irradiation to achieve bending in a desired direction. For example, it was desirable to carry out laser irradiation from an opposite direction, when an excessive deformation has occurred, so as to return the excessive deformation, however, there was an irradiation barrier and also production efficiency was low.
3) In order to obtain a high accuracy, an irradiation time period had to be elongated, thereby deteriorating production efficiency. Even if energy unit for irradiating a laser beam can be reduced, it took a long time to achieve a large deformation. Thus, production efficiency was low in a probe card having many pins, and there was a problem in that a manufacturing cost and a manufacturing time are very much larger than a conventional manufacturing method.
4) Many materials used for needles of a probe card especially in 3) are special materials, and metal materials (a tungsten alloy such as tungsten or tungsten rhenium) having a high hardness and a high melting point are mainly used. In order to obtain a desired displacement with such a meal material, a large energy must be applied to a part to be deformed until the part becomes a temperature at which the part is in a melted or half-melted state (when heat radiation to atmosphere is taken in consideration). However, with such a large energy, it was difficult to perform a fine displacement control after reaching a temperature close to a melting point and it becomes sensitively displaceable in response to the input energy.
5) Many probe needles have a rod-like shape, and their surfaces to which a laser is irradiated are curved surfaces. For this reason, relationships between an amount of laser irradiation and each of a displacement and a direction of displacement were hardly predicted, and it was difficult to displace the probe needles to target positions. Especially, many probe needles have a configuration in which a diameter decreases toward an end thereof, and, thus, a radius of curvature varies in response to a distance from a needle tip, which makes it difficult to positively displace with one""s aim.
It is a general object of the present invention to provide an improved and useful manufacturing method of a contactor in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a manufacturing method of a contactor in which contact electrodes having a predetermined shape are formed by irradiating a laser beam onto the contact electrodes that are formed of a conductive material.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a manufacturing method of a contactor for making a contact with electrodes of an electronic component, the manufacturing method comprising a step of forming at least one contact electrode by irradiating a laser beam onto the contact electrode made of a conductive material so as to deform the contact electrode in a predetermined shape.
According to the above-mentioned invention, the contact electrode of the contactor can be deformed not by mechanical processing but in a non-contact manner. Thus, a contactor having many contact electrodes arranged at a small pitch can be easily produced without physical restriction due to mechanical processing.
In the manufacturing method of a contactor according to the present invention, the step of forming the contact electrode may include a step of irradiating a laser beam, after joining an end of the contact electrode opposite to a contact end to a contact board, so as to deform said contact electrode so that the contact end is located at a predetermined position. Additionally, the laser beam may be irradiated while heating or cooling a portion of the contact electrode opposite to a portion onto which the laser beam is irradiated. Further, a plurality of the contact electrodes may be attached to a contactor board in an aligned and upright state, and thereafter the laser beam may be irradiated onto one of the contactor electrodes located at an end of a row in an upper oblique direction so as to bend the one of the contactor electrodes in the laser irradiating direction, and, then, the laser beam may be irradiated onto an adjacent contact electrode in the same row in the same direction as the direction of the laser beam irradiated onto the one of the contact electrodes located at the end of the row so as to bend the adjacent one of the contact electrodes, and repeats the laser irradiation until all of said contact electrodes are bent. Additionally, a plurality of the contact electrodes may be attached to a contactor board, and, thereafter, the laser beam may be irradiated onto each of the contact electrodes in a state in which the contactor electrodes are pressed against a flat plate to deform the contact electrodes, thereby aligning ends of the contact electrodes at the same level.
Additionally, there is provided according to another aspect of the present invention a contactor for making a contact with electrodes of an electronic component, comprising: a contactor board; and at least one contact electrode having a portion deformed by laser processing.
In the above-mentioned invention, the contact electrode may have a flat portion, and the contact electrode may be deformed by a laser beam irradiated onto the flat portion. additionally, the contact electrode may have a center portion made of a first conductive material, the second conductive material having a melting point and a hardness higher than that of the first conductive material.
Additionally, there is provided according to another aspect of the present invention a method of repairing a contact electrode of a probe card in a non-contact manner, the method comprising the step of irradiating a laser beam onto the contact electrode, which has been deformed, so as to restore the contact electrode in an original shape before deformation.
According to the above-mentioned invention, even if one of the contact electrodes is deformed, the deformed contact electrode can be restored to an original shape by only irradiating a laser beam, and, therefore, the contactor can be continuously used.
Additionally, there is provided according to another aspect of the present invention a prober for testing an electronic component, comprising: a probe card having at least one contact electrode; a placement stage on which a test material is placed, the test material being contacted by the contact electrode of the probe card; and a laser irradiating unit attached to the placement stage, wherein when said contact electrode is deformed, a laser beam is irradiated by the laser irradiating unit so as to deform the contact electrode, thereby restoring an original shape before deformation.
According to the above-mentioned invention, even if one of the contact electrodes is deformed, the deformed contact electrode ca be repaired on the prober. Additionally, there is no need to provide separately a repair apparatus.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.